This simple Morse Code oscillator was found in a 1980s American documentation. The power supply should be powered with 5V and the integrated can be the 7400.
This circuit is used in the analog part of the telephone lines. The same circuit can directly...
This circuit is from Popular Electronics from the 90's. The circuit discharges the battery with a...
The circuit shown here uses a flip-flop found inside the 4048 to divide the original frequency...